Speaker
Description
We calculate accretion mass of interstellar objects (ISOs) like Oumuamua onto low-mass population III stars (Pop. III survivors), and estimate surface pollution of Pop. III survivors. An ISO number density estimated from the discovery ofOumuamua is so high ($\sim 0.2$ au$^{-3}$) that Pop.~III survivors have chances at colliding with ISOs about $10^5$ times per $1$~Gyr. `Oumuamua itself would be sublimated near Pop.~III survivors, since it has small size, $\sim 100$ m. However, ISOs with size $\ge 3$ km would reach the Pop. III survivor surfaces. Supposing an ISO cumulative number density with size larger than $D$ is $n \propto D^{-\alpha}$, Pop. III survivors can accrete ISO mass $\ge 10^{-16}M_\odot$, or ISO iron mass $\ge 10^{-17}M_\odot$, if $\alpha < 4$. This iron mass is larger than the accretion mass of interstellar medium (ISM) by several orders of magnitude. Taking into account material mixing in a convection zone of Pop.~III survivors, we obtain their surface pollution is typically [Fe/H] $\le -8$ in most cases, however the surface pollution of Pop.~III survivors with $0.8M_\odot$ can be [Fe/H] $\ge -6$ because of the very shallow convective layer. We first show the importance of ISOs for the metal pollution of Pop.~III survivors.
Affiliation
The University of Tokyo
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